Grouping is a monitoring aid, not an alerting system. Signatures are grouped client-side from the live stream; first-seen/count are for THIS session (rebuilt from the ~24h backfill on reload). Mute/resolve persist in this browser only. A regression that both fires and fully stops while this page is closed (beyond the backfill window) is not caught. "All failures" means all the telemetry sink forwards (Level≥Information from a mapped source).